1. Field of the Invention
The present invention relates to a cleaning apparatus for cleaning and removing contaminants from a forming wire of a paper machine.
More specifically, the present invention relates to a cleaning apparatus which includes a shower and a flow of pressurized air for cleaning and removing contaminants from a forming wire of a paper machine.
2. Information Disclosure Statement
Paper is formed by ejecting a slurry of stock between converging forming wires of a paper machine.
Typically, the aforementioned twin wire formers and other types of formers are designed to operate 24 hours a day. However, contaminants from the stock tend to lodge between the interstices of the porous wires.
The uniformity of the forming wire has a significant influence on the uniformity, and therefore the quality of the sheet of paper being made on the wire. Over the long term, non-uniformity can develop in the wire as it becomes randomly clogged by fibers and additives.
Continuously running water showers are used to assist in keeping the fabric clean and to prevent clogging. Much of the water sprayed on the fabric blows through the wire and out the opposite side. Some of the water, however remains in the fabric. The water in the fabric affects drainage from the pulp slurry when it is first introduced on the machine. A non-uniform water distribution leads to a non-uniform web.
One method of preventing a non-uniform water distribution is to use an air jet to blow the shower of water out of the fabric. U.S. Pat. No. 5,381,580 assigned to Voith teaches the aforementioned air jet fabric cleaner and one method of applying an air jet in conjunction with a water shower to clean and dry the wire.
In the design illustrated in U.S. Pat. No. 5,381,580, both of the lands forming the air jet slidingly contact the forming wire. There are several disadvantages with such a design. First, to minimize air usage, the slot must be narrow. However, a narrow slot provides limited dwell time of the wire in the jet. Therefore, the cleaning and drying performance of such cleaning apparatus is adversely affected.
Another disadvantage of the aforementioned arrangement is that with two lands, two wear surfaces are touching the fabric. The incoming surface benefits from the lubricating effect of the cleaning water from the shower. However, if the air jet accomplishes its designed objective, the outgoing or downstream blade has no water for lubrication. Consequently, frictional wear on the wire by the downstream blade decreases the life of the forming wire.
In order to minimize the aforementioned friction between the blades and the wire, the distance that the blades can be pushed into the wire must be minimized. As a consequence, the jet air pressures must be kept as low as possible to prevent pushing the fabric away from the blades.
When air usage is extremely high, the air jet is extreme loud. Furthermore, a substantial amount of water mist is generated.
Additionally, ceramic coatings must be used on both blades in order to minimize friction and this adds to the cost of the end product.
The cleaning apparatus according to the present invention provides an air slot length which is considerable thus allowing an increased fabric or wire dwell time under the air jet.
Also, the present invention provides a cleaning apparatus in which the air slot length and fabric dwell time under the jet can be separately adjusted.
The cleaning apparatus according to the present invention overcomes the shortcomings of the prior art arrangement which require both blades to touch the forming wire.
Accordingly, a primary objective of the present invention is to provide a cleaning apparatus which overcomes the aforementioned problems associated with the prior art arrangements and which makes a considerable contribution to the art of removing contaminants from a forming wire of a paper machine.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.